1. Field of Invention
The present invention relates to head driving devices and methods, droplet ejecting apparatuses, head driving programs, device manufacturing methods, and devices. More particularly, the present invention relates to a head driving device and method for driving a head that ejects a highly viscous body, such as a liquid resin having high viscosity, a droplet ejecting apparatus including the head driving device, a head driving program, a device manufacturing method including, as one step, a step of ejecting a viscous body using the above-described method and manufacturing a liquid crystal display, an organic EL (Electroluminescence) display, a color filter substrate, a microlens array, an optical device having a coating layer, and other devices, and a device thereof.
2. Description of Related Art
Recently, various electronic devices, such as computers and handheld information devices, have been advancing greatly. In accordance with the advancement of the electronic devices, electronic devices having liquid crystal displays, and particularly color liquid crystal displays showing high display performance, have been increasing in number. Despite their size, color liquid crystal displays are capable of having a high display performance, and therefore applications for such devices have been expanding. A color liquid crystal display has a color filter substrate for colorizing an image to be displayed. Various methods for manufacturing the color filter substrate have been proposed. One such method proposed is a droplet ejecting method for causing R (red), G (green), and B (blue) droplets to land on the substrate in a predetermined pattern.
A droplet ejecting apparatus implementing the droplet ejecting method has a plurality of droplet ejecting heads that eject droplets. The droplet ejecting heads each have a fluid chamber for temporarily accumulating an external droplet, a piezoelectric element serving as a drive source that pressurizes a fluid in the fluid chamber to eject a predetermined amount of the fluid, and a nozzle face having a nozzle drilled therein, from which the droplet from the fluid chamber is ejected. These droplet ejecting heads are disposed at equal pitches and thus make a head group. While the head group scans the substrate along a scanning direction (for example, X direction), the droplets are ejected. As a result, the R, G, and B droplets land on the substrate. In contrast, the positional adjustment on the substrate in the direction orthogonal to the scanning direction (for example, Y direction) is made possible by moving a platform on which the substrate is placed.
The manufacture of the color filter substrate included in the above-described color liquid crystal display more often uses a highly viscous body having a higher viscosity than that of ink for use in color printers used at home. Since a less viscous body (for example, a viscous body having a viscosity of approximately 3.0 [mPaxc2x7s (millixc2x7Pascalxc2x7second)] at room temperature (25xc2x0 C.)) has a low viscosity resistance, the color printer used at home can eject a necessary amount of droplet even when a driving period of a piezoelectric element is short (for example, a few microseconds). Because the color printer used at home is required to achieve high-speed printing, a head driving device that drives a droplet ejecting head is designed to vibrate the piezoelectric element at high speed in order to achieve high-speed printing.
For example, a known head driving device includes a drive signal generator for receiving data that indicates the amount of change in voltage value of a drive signal applied to the piezoelectric element per reference clock and a clock signal that defines a period during which the voltage value of the drive signal is changed and for generating the drive signal on the basis of the data and the clock signal in synchronization with the reference clock. The reference clock input to the drive signal generator has a frequency of approximately 10 MHz. The data is a signed digital signal having approximately 10 bits. Until the above-described clock signal is input to the drive signal generator, the drive signal generator adds the value of the input data every time the reference clock is input, thereby generating a rising or falling waveform of the drive signal.
In the known head driving device, a drive signal having a steeply rising or falling waveform is generated by greatly increasing or decreasing the value of the data input to the drive signal generator. For example, when the data having the maximum value or minimum value (negative value) is input to the drive signal generator, a drive signal that suddenly rises or falls over the time of one cycle of the reference clock is generated. As a matter of fact, since a D/A converter disposed between the drive signal generator and the piezoelectric element has a response delay, the period during which the drive signal rises or falls is longer than the time of one cycle of the reference clock.
In contrast, a drive signal having a gradually rising or falling waveform is generated by decreasing the value of the data input to the drive signal generator and by inputting the clock signal at a later time. In order to simplify the description, it is assumed that the data is an unsigned 10-bit digital signal. In this case, there are 210=1024 possible combinations for the value of the drive signal. When the data having the minimum value is input in order to generate a gradually rising waveform, the voltage value of the drive signal changes from the minimum value to the maximum value over a period of 1024 clocks of the reference clock. When the reference clock is at 10 MHz, the time of one cycle is 0.1 xcexcs. Theoretically speaking, the period during which the drive signal rises or falls is variable within the range from approximately 0.1 to 102.4 xcexcs.
As described above, a highly viscous body is used in the droplet ejecting apparatus for use in manufacturing a color filter substrate. It is thus necessary to vibrate the piezoelectric element for a long period of time in order to eject a necessary amount of droplet. For example, the manufacture of a color filter involves vibrating the piezoelectric element for a few milliseconds. The manufacture of a microlens involves vibrating the piezoelectric element for a long period of time of approximately one second. As described above, the known head driving device is designed to vibrate the piezoelectric element at high speed, and the maximum time during which the drive signal rises or falls is approximately 102.4 xcexcs. There is a problem in that the head driving device used at home cannot be simply used as the head driving device of the droplet ejecting apparatus for ejecting a highly viscous body.
This problem does not only arises in the manufacture of a color filter substrate of a liquid crystal display, but also arises in the manufacture of an organic EL (Electroluminescence) display, the manufacture of a microlens array using a highly viscous transparent liquid resin, the formation of a coating layer on the surface of an optical element such as a spectacle lens using a highly viscous liquid resin, or the like. In short, the problem is a general problem with a device manufacturing method having, as one manufacturing step, a step of ejecting a viscous body.
In view of the foregoing circumstances, it is an object of the present invention to provide a head driving device and method for ejecting a necessary amount of a viscous body from a head having a pressure generating element, such as a piezoelectric element, a droplet ejecting apparatus including the head driving device, a head driving program, a device manufacturing method including, as one manufacturing step, a step of ejecting a viscous body using the above-described method, and a device manufactured using the droplet ejecting apparatus or the device manufacturing method.
In order to solve the foregoing problems, a head driving device of the present invention is a head driving device operating in synchronization with a reference clock and ejecting a viscous body by applying a drive signal to a pressure generating element included in a head, and thus deforming the pressure generating element. The head driving device includes frequency changing means for changing the frequency of the reference clock in accordance with a deformation rate of the pressure generating element per unit time.
According to the present invention, the frequency of the reference clock that defines the operation timing of the head driving device that generates the drive signal applied to the pressure generating element can be changed in accordance with the deformation rate of the pressure generating element per unit time. Both the drive signal whose value gradually changes and the drive signal whose value suddenly changes in accordance with the frequency of the reference clock are easily generated. As a result, the deformation rate of the pressure generating element per unit time is easily controlled.
In order to eject a necessary amount of a highly viscous body, the viscous body needs to be gradually pulled into the head and then ejected at a certain degree of speed. The pressure generating element thus needs to be gradually deformed and then to be quickly restored. According to the present invention, both the drive signal whose value gradually changes and the drive signal whose value suddenly changes in accordance with the frequency of the reference clock are easily generated. The present invention is thus highly suitable to ejecting the viscous body.
In the head driving device of the present invention, the frequency changing device can change the frequency of the reference clock by dividing the reference clock.
According to the present invention, the frequency of the reference clock can be changed by dividing the reference clock. Changing the frequency of the reference clock does not involve a great change in the device configuration. As a result, the implementation of the present invention requires almost no increase in the cost. As discussed above, the present invention is implementable using some of the configuration of a known device. By using the known device, the resource can be utilized.
In the head driving device of the present invention, preferably the deformation rate of the pressure generating element (48a) per unit time is set in accordance with the viscosity of the viscous body. It is preferable that the viscosity of the viscous body be within the range from 10 to 40000 [mPaxc2x7s] at room temperature (25xc2x0 C.).
According to the present invention, setting the deformation rate of the pressure generating element per unit time in accordance with the viscosity of the viscous body makes it possible to perform a variety of control modes, such as deforming a highly viscous body over a long period of time while deforming a less viscous body over a short period of time. Such control modes are highly suitable to ejecting a necessary amount of viscous body.
In the head driving device of the present invention, the pressure generating element (48a) includes a piezoelectric vibrator that generates stretching vibrations or flexible vibrations upon application of the drive signal (COM) and pressurizes the viscous body. According to the present invention, both the head having the piezoelectric vibrator that generates stretching vibrations and that serves as the pressure generating element and the head having the piezoelectric vibrator that generates flexible vibrations and that serves as the pressure generating element are driven. The present invention is thus applicable to various devices without involving a great change in the device configuration.
The head driving device of the present invention further includes a drive signal generator that generates, when intermittently applying the drive signal to the pressure generating element, the drive signal including an auxiliary drive signal for setting the surface state of the viscous body to a predetermined state. According to the present invention, the pressure generating element is driven by the drive signal that includes the auxiliary drive signal for setting the surface state of the viscous body to the predetermined state. When the viscous body is ejected, the surface state of the viscous body is maintained at the predetermined state. This is very advantageous in continuously ejecting a necessary amount of the viscous body.
In order to solve the foregoing problems, a head driving method of the present invention is a head driving method for a head driving device operating in synchronization with a reference clock and ejecting a viscous body by applying a drive signal to a pressure generating element included in a head and thus deforming the pressure generating element. The method includes a frequency changing step of changing the frequency of the reference clock in accordance with a deformation rate of the pressure generating element per unit time.
According to the present invention, the frequency of the reference clock that defines the operation timing of the head driving device that generates the drive signal applied to the pressure generating element is changed in accordance with the deformation rate of the pressure generating element per unit time. Both the drive signal whose value gradually changes and the drive signal whose value suddenly changes in accordance with the frequency of the reference clock are easily generated. As a result, the deformation rate of the pressure generating element per unit time is easily controlled.
In order to eject a necessary amount of highly viscous body, the viscous body needs to be gradually pulled into the head and then ejected at a certain degree of speed. The pressure generating element thus needs to be gradually deformed and then to be quickly restored. According to the present invention, both the drive signal whose value gradually changes and the drive signal whose value suddenly changes in accordance with the frequency of the reference clock are easily generated. The present invention is thus highly suitable to ejecting the viscous body.
In the head driving method of the present invention, in the frequency changing step, the frequency of the reference clock is changed by dividing the reference clock. According to the present invention, the frequency of the reference clock is changed by dividing the reference clock. The frequency of the reference clock can thus be changed without complicated control. Preferably, the head driving method of the present invention further includes a selection step of selecting a division ratio of the reference clock in accordance with the deformation rate of the pressure generating element.
In the head driving method of the present invention, preferably the deformation rate of the pressure generating element per unit time is set in accordance with the viscosity of the viscous body. It is preferable that the viscosity of the viscous body be within the range from 10 to 40000 [mPaxc2x7s] at room temperature (25xc2x0 C.).
According to the present invention, setting the deformation rate of the pressure generating element per unit time in accordance with the viscosity of the viscous body makes it possible to perform a variety of control modes, such as deforming a highly viscous body over a long period of time while deforming a less viscous body over a short period of time. Such control modes are highly suitable to ejecting a necessary amount of viscous body.
The head driving method of the present invention further includes an auxiliary drive signal applying step of applying an auxiliary drive signal for setting the surface state of the viscous body to a predetermined state prior to or subsequent to applying the drive signal for ejecting the viscous body to the pressure generating element.
According to the present invention, the pressure generating element is driven by the drive signal that includes the auxiliary drive signal for setting the surface state of the viscous body to the predetermined state. When the viscous body is ejected, the surface state of the viscous body is maintained at the predetermined state. This is very advantageous in continuously ejecting a necessary amount of the viscous body.
In order to solve the foregoing problems, a droplet ejecting apparatus of the present invention includes any one of the above-described head driving devices. According to the present invention, since the droplet ejecting apparatus includes the above-described head driving device, the droplet ejecting apparatus that ejects a necessary amount of the viscous body can be achieved without adding a great change to the configuration of the apparatus.
In order to solve the foregoing problems, a head driving program of the present invention is a program for performing any one of the above-described head driving methods.
In order to solve the foregoing problems, a device manufacturing method of the present invention includes, as one device manufacturing step, a step of ejecting a viscous body using any one of the above-described head driving methods. According to the present invention, since necessary amounts of various viscous bodies can be ejected, devices according to various specifications can be manufactured.
In order to solve the foregoing problems, a device of the present invention is manufactured using the above-described droplet ejecting apparatus or the above-described device manufacturing method. According to the present invention, since a device is manufactured using the apparatus or method that can eject necessary amounts of various viscous bodies, devices according to various specifications can be manufactured.